The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Thomas H Deluca - One of the best experts on this subject based on the ideXlab platform.
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the influence of fire history on soil nutrients and vegetation cover in mixed severity fire regime forests of the eastern olympic peninsula washington usa
Forest Ecology and Management, 2018Co-Authors: Melissa R A Pingree, Thomas H DelucaAbstract:Abstract The rain shadow forests of the Olympic Peninsula exemplify a mixed-severity fire regime class in the midst of a highly productive landscape where spatial heterogeneity of fire severity may have significant implications for below and aboveground post-fire recovery. The purpose of this study was to quantify the impacts of wildfire on forest soil carbon (C) and nitrogen (N) pools and assess the relationship of pyrogenic carbon (PyC) to soil processes in this mixed-severity ecosystem. We established a 112-year fire chronosequence with nine similar forest stands ranging in time since lastfire (TSF) from 3 to 115 years prior to site establishment. At each site, we measured understory vegetation cover, overstory composition, physical and chemical attributes of surface Mineral Soils to a depth of 10 cm, and forest floor organic matter. Additionally, non-ionic resin lysimeters were buried over the winter and spring (7–8 months) at the interface of organic and Mineral soil to collect O-horizon leached DOC that would potentially contact PyC particles on the forest floor. Nitrogen transformations were also monitored in laboratory soil incubations for a subset of sites. The TSF gradient was significantly correlated with PyC mass in the O-horizon (r = −0.4), O-horizon C (r = 0.4), total phenol content in both O-horizon (r = 0.4) and Mineral Soils (r = 0.2), and potentially Mineralizable N (PMN) (r = 0.4). Recent fire sites contained higher Mineral soil total N and inorganic available N, but were not correlated with TSF. Total DOC that accumulated on the non-ionic resins averaged 1.14 (SE ± 0.54) g DOC m−2 year−1 and increased with TSF (r = 0.52; p
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the influence of fire history on soil nutrients and vegetation cover in mixed severity fire regime forests of the eastern olympic peninsula washington usa
Forest Ecology and Management, 2018Co-Authors: Melissa R A Pingree, Thomas H DelucaAbstract:Abstract The rain shadow forests of the Olympic Peninsula exemplify a mixed-severity fire regime class in the midst of a highly productive landscape where spatial heterogeneity of fire severity may have significant implications for below and aboveground post-fire recovery. The purpose of this study was to quantify the impacts of wildfire on forest soil carbon (C) and nitrogen (N) pools and assess the relationship of pyrogenic carbon (PyC) to soil processes in this mixed-severity ecosystem. We established a 112-year fire chronosequence with nine similar forest stands ranging in time since lastfire (TSF) from 3 to 115 years prior to site establishment. At each site, we measured understory vegetation cover, overstory composition, physical and chemical attributes of surface Mineral Soils to a depth of 10 cm, and forest floor organic matter. Additionally, non-ionic resin lysimeters were buried over the winter and spring (7–8 months) at the interface of organic and Mineral soil to collect O-horizon leached DOC that would potentially contact PyC particles on the forest floor. Nitrogen transformations were also monitored in laboratory soil incubations for a subset of sites. The TSF gradient was significantly correlated with PyC mass in the O-horizon (r = −0.4), O-horizon C (r = 0.4), total phenol content in both O-horizon (r = 0.4) and Mineral Soils (r = 0.2), and potentially Mineralizable N (PMN) (r = 0.4). Recent fire sites contained higher Mineral soil total N and inorganic available N, but were not correlated with TSF. Total DOC that accumulated on the non-ionic resins averaged 1.14 (SE ± 0.54) g DOC m−2 year−1 and increased with TSF (r = 0.52; p
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Estimating charcoal content in forest Mineral Soils
Geoderma, 2006Co-Authors: Valerie J. Kurth, M D Mackenzie, Thomas H DelucaAbstract:Abstract Traditional methods for estimating charcoal in Soils can be time consuming, expensive, and not entirely quantitative. A standard analytic method that is inexpensive, rapid, and simple would be of great value to scientists needing to quantify charcoal in Soils or sediment. Preliminary laboratory investigations analyzed the efficacy of several digestion methods for the determination of the charcoal content of Soils. Concentrated nitric acid digestions were found to consume a portion of the charcoal leading to an underestimation of soil charcoal content by as much as 70%. Herein we test two alternative approaches to the determination of charcoal content of forest Soils. Subsurface soil samples (60–120 cm) were taken from areas not exposed to fire (charcoal deposition) for 100 years and amended with charcoal ranging in content from 0–50 g kg− 1. Samples were analyzed using two different approaches: the Walkley–Black method and a digestion using 30% H2O2 and dilute (1 M) HNO3. Using the Walkley–Black method, organic C, measured by colorimetry, was subtracted from total C, measured by dry combustion, to estimate total charcoal content. This method estimated about 80% of soil charcoal, which is an improvement over current digestion methods, but was found to be unreliable for Soils containing less than 0.5% (w/w) or 5 g kg− 1charcoal. The H2O2/dilute HNO3 digestion effectively estimated soil charcoal contents in Soils with 0.5% to 5% (w/w) charcoal, and had substantially less variation than the Walkley–Black method. This new digestion procedure shows promise for estimation of total charcoal contents of soil and can be used in paleoecological evaluation of charcoal in Mineral soil or sediment.
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prescribed fire alters the impact of wildfire on soil biochemical properties in a ponderosa pine forest
Soil Science Society of America Journal, 2001Co-Authors: U Choromanska, Thomas H DelucaAbstract:Although studies have addressed the influence of fire on soil biochemical processes, there have been no reports on how prescribed fire followed by wildfire influences microbial activity and nutrient cycling. Over a 21-mo period we monitored changes in soil nitrogen (N) and carbon (C) of a ponderosa pine (Pinus ponderosa P.&C. Lawson) and Douglas-fir [Pseudotsuga menziesii var. glauca (Beissn.) Franco] forest (both O horizon and 0-10 cm of Mineral soil) that had been exposed either to prescribed fire (PB), wildfire (WF), prescribed fire three months prior to wildfire (PBWF), or no fire as an unburned control. Total N, potentially Mineralizable N (PMN), NH 4 + -N and NO 3 - -N concentrations in surface (0-10 cm) Mineral Soils were significantly increased immediately after WF. Soils exposed to prescribed fire prior to wildfire also had elevated concentrations of total N, PMN and NH 4 + -N, but were significantly lower than in WF alone. Potentially Mineralizable N was significantly reduced on all fire-exposed sites from 9 mo to the end of the study period. Although Mineral soil NO 3 - -N concentrations in fire-exposed Soils were similar to the unburned control 12 mo after fire, resin sorbed NO 3 - -N was 88 μg capsule -1 in WF Soils vs. 24 eg capsule -1 in PBWF Soils, and 1.3 μg capsule -1 in the unburned control. Microbial biomass in the WF Mineral Soils was as low as 52 μg g -1 21 mo after fire while microbial biomass in PBWF Soils remained above 100 μg g -1 throughout the study. It appears that prescribed fire prior to wildfire may attenuate the effects of wildfire on soil and may have predisposed the microbial community to the effects of heating.
Don A. Cowan - One of the best experts on this subject based on the ideXlab platform.
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hypolithic communities important nitrogen sources in antarctic desert Soils
Environmental Microbiology Reports, 2011Co-Authors: Don A. Cowan, Thulani P Makhalanyane, Stephen C Cary, Jill A. Sohm, T. G. A. Green, Douglas G Capone, I M TuffinAbstract:Summary Hypolithic microbial communities (i.e. cryptic microbial assemblages found on the undersides of translucent rocks) are major contributors of carbon input into the oligotrophic hyper-arid desert Mineral Soils of the Eastern Antarctic Dry Valleys. Here we demonstrate, for the first time, that hypolithic microbial communities possess both the genetic capacity for nitrogen fixation (i.e. the presence of nifH genes) and the ability to catalyse acetylene reduction, an accepted proxy for dinitrogen fixation. An estimate of the total contribution of these communities suggests that hypolithic communities are important contributors to fixed nitrogen budgets in Antarctic desert Soils.
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phylogenetic analysis of actinobacterial populations associated with antarctic dry valley Mineral Soils
Environmental Microbiology, 2009Co-Authors: Olubukola Oluranti Babalola, Bronwyn M Kirby, Marilize Le Roeshill, Andrew E Cook, Craig S Cary, Stephanie G Burton, Don A. CowanAbstract:Despite the apparent severity of the environmental conditions in the McMurdo Dry Valleys, Eastern Antarctica, recent phylogenetic studies conducted on Mineral soil samples have revealed the presence of a wide diversity of microorganisms, with actinobacteria representing one of the largest phylotypic groups. Previous metagenomic studies have shown that the majority of Antarctic actinobacterial populations are classified as 'uncultured'. In this study, we assessed the diversity of actinobacteria in Antarctic cold desert Soils by complementing traditional culture-based techniques with a metagenomic study. Phylogenetic analysis of clones generated with actinobacterium- and streptomycete-specific PCR primers revealed that the majority of the phylotypes were most closely related to uncultured Pseudonocardia and Nocardioides species. Phylotypes most closely related to a number of rarer actinobacteria genera, including Geodermatophilus, Modestobacter and Sporichthya, were also identified. While complementary culture-dependent studies isolated a number of Nocardia and Pseudonocardia species, the majority of the cultured isolates (> 80%) were Streptomyces species--although phylotypes affiliated to the genus Streptomyces were detected at a low frequency in the metagenomic study. This study confirms that Antarctic Dry Valley desert soil harbours highly diverse actinobacterial communities and suggests that many of the phylotypes identified may represent novel, uncultured species.
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bacterial diversity in three different antarctic cold desert Mineral Soils
Microbial Ecology, 2006Co-Authors: Jacques J Smith, William Stafford, Craig Cary, Don A. CowanAbstract:A bacterial phylogenetic survey of three environmentally distinct Antarctic Dry Valley soil biotopes showed a high proportion of so-called “uncultured” phylotypes, with a relatively low diversity of identifiable phylotypes. Cyanobacterial phylotypic signals were restricted to the high-altitude sample, whereas many of the identifiable phylotypes, such as the members of the Actinobacteria, were found at all sample sites. Although the presence of Cyanobacteria and Actinobacteria is consistent with previous culture-dependent studies of microbial diversity in Antarctic Dry Valley Mineral Soils, many phylotypes identified by 16S rDNA analysis were of groups that have not hitherto been cultured from Antarctic Soils. The general belief that such “extreme” environments harbor a relatively low species diversity was supported by the calculation of diversity indices. The detection of a substantial number of uncultured bacterial phylotypes showing low BLAST identities (<95%) suggests that Antarctic Dry Valley Mineral Soils harbor a pool of novel psychrotrophic taxa.
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antarctic dry valley Mineral Soils contain unexpectedly high levels of microbial biomass
Extremophiles, 2002Co-Authors: Don A. Cowan, Nicholas J Russell, Adam Mamais, Devon M SheppardAbstract:We have applied bioluminescent ATP detection methods to microbial enumeration in Antarctic Dry Valley Mineral Soils, and validated our ATP data by two independent methods. We have demonstrated that ATP measurement is a valid means of determining microbial biomass in such sites, and that the desiccated surface Mineral Soils of the Antarctic Dry Valleys contain cell numbers over four orders of magnitude higher than previously suggested.
Melissa R A Pingree - One of the best experts on this subject based on the ideXlab platform.
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the influence of fire history on soil nutrients and vegetation cover in mixed severity fire regime forests of the eastern olympic peninsula washington usa
Forest Ecology and Management, 2018Co-Authors: Melissa R A Pingree, Thomas H DelucaAbstract:Abstract The rain shadow forests of the Olympic Peninsula exemplify a mixed-severity fire regime class in the midst of a highly productive landscape where spatial heterogeneity of fire severity may have significant implications for below and aboveground post-fire recovery. The purpose of this study was to quantify the impacts of wildfire on forest soil carbon (C) and nitrogen (N) pools and assess the relationship of pyrogenic carbon (PyC) to soil processes in this mixed-severity ecosystem. We established a 112-year fire chronosequence with nine similar forest stands ranging in time since lastfire (TSF) from 3 to 115 years prior to site establishment. At each site, we measured understory vegetation cover, overstory composition, physical and chemical attributes of surface Mineral Soils to a depth of 10 cm, and forest floor organic matter. Additionally, non-ionic resin lysimeters were buried over the winter and spring (7–8 months) at the interface of organic and Mineral soil to collect O-horizon leached DOC that would potentially contact PyC particles on the forest floor. Nitrogen transformations were also monitored in laboratory soil incubations for a subset of sites. The TSF gradient was significantly correlated with PyC mass in the O-horizon (r = −0.4), O-horizon C (r = 0.4), total phenol content in both O-horizon (r = 0.4) and Mineral Soils (r = 0.2), and potentially Mineralizable N (PMN) (r = 0.4). Recent fire sites contained higher Mineral soil total N and inorganic available N, but were not correlated with TSF. Total DOC that accumulated on the non-ionic resins averaged 1.14 (SE ± 0.54) g DOC m−2 year−1 and increased with TSF (r = 0.52; p
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the influence of fire history on soil nutrients and vegetation cover in mixed severity fire regime forests of the eastern olympic peninsula washington usa
Forest Ecology and Management, 2018Co-Authors: Melissa R A Pingree, Thomas H DelucaAbstract:Abstract The rain shadow forests of the Olympic Peninsula exemplify a mixed-severity fire regime class in the midst of a highly productive landscape where spatial heterogeneity of fire severity may have significant implications for below and aboveground post-fire recovery. The purpose of this study was to quantify the impacts of wildfire on forest soil carbon (C) and nitrogen (N) pools and assess the relationship of pyrogenic carbon (PyC) to soil processes in this mixed-severity ecosystem. We established a 112-year fire chronosequence with nine similar forest stands ranging in time since lastfire (TSF) from 3 to 115 years prior to site establishment. At each site, we measured understory vegetation cover, overstory composition, physical and chemical attributes of surface Mineral Soils to a depth of 10 cm, and forest floor organic matter. Additionally, non-ionic resin lysimeters were buried over the winter and spring (7–8 months) at the interface of organic and Mineral soil to collect O-horizon leached DOC that would potentially contact PyC particles on the forest floor. Nitrogen transformations were also monitored in laboratory soil incubations for a subset of sites. The TSF gradient was significantly correlated with PyC mass in the O-horizon (r = −0.4), O-horizon C (r = 0.4), total phenol content in both O-horizon (r = 0.4) and Mineral Soils (r = 0.2), and potentially Mineralizable N (PMN) (r = 0.4). Recent fire sites contained higher Mineral soil total N and inorganic available N, but were not correlated with TSF. Total DOC that accumulated on the non-ionic resins averaged 1.14 (SE ± 0.54) g DOC m−2 year−1 and increased with TSF (r = 0.52; p
Akihiro Koyama - One of the best experts on this subject based on the ideXlab platform.
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soil bacterial community composition altered by increased nutrient availability in arctic tundra Soils
Frontiers in Microbiology, 2014Co-Authors: Akihiro Koyama, Matthew D Wallenstein, Rodney T Simpson, John C MooreAbstract:The pool of soil organic carbon (SOC) in the Arctic is disproportionally large compared to those in other biomes. This large quantity of SOC accumulated over millennia due to slow rates of decomposition relative to net primary productivity. Decomposition is constrained by low temperatures and nutrient concentrations, which limit soil microbial activity. We investigated how nutrients limit bacterial and fungal biomass and community composition in organic and Mineral Soils within moist acidic tussock tundra ecosystems. We sampled two experimental arrays of moist acidic tussock tundra that included fertilized and non-fertilized control plots. One array included plots that had been fertilized annually since 1989 and the other since 2006. Fertilization significantly altered overall bacterial community composition and reduced evenness, to a greater degree in organic than Mineral Soils, and in the 1989 compared to the 2006 site. The relative abundance of copiotrophic α-proteobacteria and β-proteobacteria was higher in fertilized than control Soils, and oligotrophic Acidobacteria were less abundant in fertilized than control Soils at the 1989 site. Fungal community composition was less sensitive to increased nutrient availability, and fungal responses to fertilization were not consistent between soil horizons and sites. We detected two ectomycorrhizal genera, Russula and Cortinarius spp., associated with shrubs. Their relative abundance was not affected by fertilization despite increased dominance of their host plants in the fertilized plots. Our results indicate that fertilization, which has been commonly used to simulate warming in Arctic tundra, has limited applicability for investigating fungal dynamics under warming.
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fire effects on gross inorganic n transformation in riparian Soils in coniferous forests of central idaho usa wildfires v prescribed fires
International Journal of Wildland Fire, 2012Co-Authors: Akihiro Koyama, Kirsten Stephan, Kathleen L KavanaghAbstract:We investigated differences between wildfires and prescribed fires in their effects on nitrogen (N) dynamics in Mineral Soils collected from riparian coniferous forests of central Idaho, USA. Specifically, we investigated how the two types of fires affected inorganic N concentrations, microbial biomass N and gross transformation rates of inorganic N in Mineral Soils relative to their corresponding unburnt controls. There was no significant difference in soil NH4+ concentrations between burnt and control Soils in either type of fires. However, wildfires significantly reduced gross ammonification and microbial NH4+ uptake rates relative to their controls (P = 0.05 and 0.08). No such effect was found in Soils burnt by the prescribed fires relative to their controls. Burnt Soils had significantly higher NO3– concentrations than control Soils when all the data were pooled (P = 0.08). The elevated NO3– concentrations in the Soils burnt by either type of fire were not caused by increased gross nitrification, but likely by significantly reduced microbial NO3– uptake (P ≤ 0.02). We concluded that controlled prescribed fires conducted in early spring had less of an effect on soil N dynamics than wildfires in the region.
Steven J Hall - One of the best experts on this subject based on the ideXlab platform.
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elevated moisture stimulates carbon loss from Mineral Soils by releasing protected organic matter
Nature Communications, 2017Co-Authors: Wenjuan Huang, Steven J HallAbstract:Moisture response functions for soil microbial carbon (C) Mineralization remain a critical uncertainty for predicting ecosystem-climate feedbacks. Theory and models posit that C Mineralization declines under elevated moisture and associated anaerobic conditions, leading to soil C accumulation. Yet, iron (Fe) reduction potentially releases protected C, providing an under-appreciated mechanism for C destabilization under elevated moisture. Here we incubate Mollisols from ecosystems under C3/C4 plant rotations at moisture levels at and above field capacity over 5 months. Increased moisture and anaerobiosis initially suppress soil C Mineralization, consistent with theory. However, after 25 days, elevated moisture stimulates cumulative gaseous C-loss as CO2 and CH4 to >150% of the control. Stable C isotopes show that Mineralization of older C3-derived C released following Fe reduction dominates C losses. Counter to theory, elevated moisture may significantly accelerate C losses from Mineral Soils over weeks to months—a critical mechanistic deficiency of current Earth system models.